Hypogonadism results in a high turnover bone loss; the rate of bone loss in women after menopause has been studied, but the rate of bone loss in men with hypogonadism due to surgical or chemical castration is unknown. This study is designed to assess the rate of bone loss in men immediately following surgical or medical castration because of prostate cancer. Men who are scheduled to undergo surgical orchietomy or medical castration and normal age-matched controls will be studied. Bone mineral density measurements will be determined at baseline, 6 and 12 months.